IRVING (CBSDFW.COM) – Rumors, security concerns and the arrest of a student at Nimitz High School in Irving — all events that made for a very tense day for students and parents.

There was nothing surprising about administrators releasing students for the week at Nimitz, but the number of police officers on campus was definitely different.

CBS 11 News got a copy of the letter sent home to parents explaining that the concerns on campus Friday were centered around rumors.

The rumors centered on a brawl that happened between two groups, at nearby Fritz Park, earlier this week. Irving police said it was believed there was a retaliation issue and that the groups were going to fight again and shoot at each other at Nimitz High.

Student Pablo Vera told CBS 11 News, “Supposedly they were going to shoot after school and during the cafeteria.”

School officials say the rumors spread by way of mouth and all over social media. Once the information made it to police and school officials action was quickly taken to beef up security, send those letters and make robo calls home to parents.

Nimitz student Aaron Valles was certainly apprehensive. “They say it’s rumors but I don’t know if something is really going to go down or not. It’s crazy in there.”

More than 100 parents showed up to check their kids out of school early. Margarita Castanon picked up her little sister. “They actually gave us a paper stating it was just rumors. My mom just wanted her to be safe. So we just came by to get her,” she said.

One student on the campus was arrested for not consenting to a search. We’re told police did find a small pocketknife on the teen, and it’s unknown if he had anything to do with the past fight or rumors that disrupted the day Friday.

No shoot out happened and no student was hurt by the end of the school day on Friday.

Both police and administrators say they will continue investigating the rumors through the weekend and into Monday.